An inherent characteristic of the refrigerant compressor, such as used in an automotive air conditioning system, is the generation of dynamic pressure fluctuations, or pulsations, due to the dynamics of the compression process and interaction of the gaseous refrigerant flow between the cylinders in the compressor. These pressure pulsations have the undesirable effect of exciting certain components in the automotive air conditioning system, as well as components in the vehicle structure, which result in objectionable noise and/or vibration. Also, the vibrating and rattling components are prone to rapid wear and premature failure.
The prior art has attempted to solve this problem by installing a pressure pulsation muffler in the discharge conduit extending from the compressor to the air conditioning condenser. However, the inline mounted mufflers are expensive and require considerable additional space. The prior art also teaches that pressure pulsations may be attenuated by enlarging the volume of the compressor discharqe plenum, or cavity, which, due to the expansion characteristics of refrigerant gas, will act to absorb some of the pressure pulsations. However, this prior art attempt to alleviate the pressure pulsation problem is also undesirable because an enlarged discharge cavity for the refrigerant compressor requires precious additional space and significantly increases the cost of the compressor.
Further, the prior art has attempted to alleviate the pressure pulsation problem by adding a gas flow restriction within the discharge cavity, as shown in the U.S. Pat. No. 4,715,790 to Iijima et al, issued Dec. 29, 1987. However, this method of gas pulsation suppression becomes particularly disadvantageous at high operating speeds, where the added pressure drop in the discharge cavity due to the orifice restriction significantly increases the discharge pressure within the discharge cavity, having the result of raising the pressures in the discharge cavity toward the critical limit of the surrounding materials, thereby significantly reducing the durability of the compressor.